The present invention relates to an apparatus and a method for inspecting defects for the purpose of detecting a small pattern defect and foreign substance of an inspection subject.
On the manufacturing line of semiconductor substrates or the thin film substrates, the inspection with respect to defects on the surface of the semiconductor substrate or the thin film substrate has been conducted so as to maintain and improve yield of the product.
Patent Literature 1 (Japanese Patent Laid-Open No. 05-264467) discloses “a defect inspection apparatus for inspecting the defect of repeated pattern through the process of comparing a first multiple-value digital signal obtained by delaying the multiple-value digital signal by an amount corresponding to the pitch of the repeated pattern, and a simultaneously converted second multiple-value digital signal, detecting a spatially corresponding positional deviation of the digital signals between the first and the second multiple-values, and adjusting an amount of delay performed by a delay unit so that the positional deviation is optimized” as the related art technique for carrying out the defect detection through comparison between the detected image and the reference image. Patent Literatures 2 (U.S. Pat. No. 7,221,992) and 3 (US 2008/0285023) disclose the method “for discrimination between the defect and noise through the process of simultaneously detecting images under plural different optical conditions, making a comparison with respect to luminance between the image and the reference image, and integrating the resultant comparative values”.